And we turn next to a story affecting every american family. Here's the question. Are your earphones ruining your hearing? Right now, tonight? Are millions and millions of americans walking around, listening to music, but ensuring they will not be able to hear as well in the years ahead? Tonight, the mayor of new york says it's time to send out an alarm. And abc's chief medical editor dr. Richard besser is stepping in. Reporter:30 years ago, PEOPLE IN THEIR 20s COULD ALL Hear the rustle of leaves. The drip of a raindrop. The babble of children. Now, for 1 in 5 of them, those sounds are gone, forever. People were coming in in THEIR 50s AND 60s WITH HEARING Loss. Now, that has shifted into PEOPLE IN THEIR 30s AND 40s. Reporter: In fact, dr. George alexiades has to tell more and more teens their high pitched hearing is already gone. Designer headphones are big business. High ticket must haves. Butt for hearing loss, ear bumds may be the most destructive. Music devices can produce about 115 decibels of sound. Earbumds addmore. 85 decibels is where hearing damage starts. Poumer times? 98 decibels. A lawn mower? 107. A jet taking off, 100 feet away? 140. So, how loud is the music? I went out with a decibel meter. Coming in about 95. Oh. Reporter:105. Whoa. Reporter:109. Oh, my god. Reporter: Here's what happens inside your ear. When strong sound vibrations hit your ear, the problem, deep inside the coke lea, are fragile cells. Blast them with loud sounds and some wither. If the loud sound is brief, they If it happens too off, they die. And they never grow back. If you get to 100 decibels, i would limit that to about one hour a day. Reporter: My advice? Never go higher than three quarters of your top volume. And a couple of hours is enough. Dr. Richard besser, abc news, new york.

This transcript has been automatically generated and may not be 100% accurate.

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